The High Resolution Dynamics
Limb Sounder (HIRDLS) is a spaceborne infrared limb-scanning radiometer
designed to sound the upper troposphere, stratosphere, and mesosphere to
determine temperature; the concentrations of O3, H2O, CH4, N2O, NO2, HNO3, N2O5, ClONO2, CFC11, CFC12, and aerosols; and the locations of cirrus
and polar stratospheric clouds and cloud tops. These are the key elements
needed to understand the chemistry and dynamics in those regions, including the
roles of planetary and gravity waves in transporting and mixing radiatively and
chemically active species important in climate change. The goals are to provide
sounding observations with horizontal and vertical resolution superior to that
previously obtained; to observe the lower stratosphere with improved
sensitivity and accuracy; and to improve understanding of atmospheric processes
through data analysis, diagnostics, and use of two- and three-dimensional
models. Development of the HIRDLS instrument is lead by the U.S. Principal
Investigator, John Gille (NCAR and the University of Colorado (CU)), and by the
U.K. Principal Investigator, John Barnett (Oxford University). HIRDLS is a
joint US-UK development effort, with sponsorship by the British National Space
Centre and the Natural Environment Research Council in the UK, and by NASA in
the US. HIRDLS is planned for flight on
the Earth Observing System Aura Mission in the year 2003.
The overall management of
HIRDLS is housed in the Center for Lower Atmospheric Studies of the University
of Colorado at Boulder. Susan Avery and
Dan Baker serve as Director and Deputy Director, respectively, of CLAS. The scope of CLAS activity changed in a
significant way this year when the Aura program at NASA’s Goddard Space Flight
Center (GSFC) decided to move the responsibility for management of the hardware
contract with Lockheed Martin Space Systems Company from CLAS to GSFC. This was done to clarify the lines of
responsibility and facilitate the use of GSFC resources to help LMSSC meet cost
and schedule requirements. As a result, CLAS responsibilities and staff have
decreased. Joanne Loh continues as
manager of the science and science computing facility activities, assisted by
Linda Henderson (Administrator) and David Wilson (Contracts, part time). Michael Dials and Douglas Woodard are
members of the instrument system engineering team, and, with Aaron Lee, work to
ensure that the instrument will meet the scientific requirements that have been
placed on it. All of the above are ACD Visitors.
NCAR, under subcontract to
CU, continues its key roles of providing scientific support to the instrument
development, leading the creation of data reduction software, and planning for
science data validation and applications.
Significant progress was
made on the instrument development this year.
Testing of the Engineering Model (EM) detector dewar and data system,
mated with the lens system, showed that the noise levels were within
specifications, with considerable margin.
The complete EM was integrated by the end of January, and performed well
in functional performance tests. A
special program review in February gave HIRDLS high marks, and cleared the way
to completion of the Proto-flight Model (PFM) that will be launched. Subsequently all efforts have gone into
completion of the 9 PFM subsystems. By
the end of the reporting period 5 have been delivered with 2 more expected
shortly. Initial testing of the
scanner, a critical component, indicates that the demanding requirements will
be met with adequate margin.
The NCAR members of the
HIRDLS Team continue to play lead roles in the design, fabrication, testing and
calibration of the HIRDLS instrument, as well as in the development of data
reduction algorithms, and data validation plans.
The effective noise due to
motions of the line of sight continued to be a source of concern. Brian Johnson analyzed results from the
spacecraft contractor which showed that most disturbances at frequencies less
than 10 Hz were due to other instruments, but were not large enough to violate
the sample spacing requirements. They
also fall within the band where they will be measured by the HIRDLS gyro. Of greater concern are the motions at
frequencies > 40 Hz excited by the spacecraft reaction wheels. Johnson showed that the new data indicate
that these are probably not large enough to cause a problem.
Alyn Lambert continued the
development of the science data retrieval algorithms, which will use the
maximum likelihood method. The
algorithm for retrieving trace species was tested on a day’s O3 and
H2O data, and showed that data in the lower stratosphere were
retrieved with only a few percent random error, as expected. Subsequently the algorithm for retrieving
temperature as a function of pressure was completed, and an algorithm for
recovery of aerosol interference was begun.
All of these used transmittance functions developed by David Edwards,
Chris Halvorson and Thomas Heineman (visitor, Freie University of Berlin,
Germany). A more detailed treatment of
the effects of gradients along the line of sight has been developed by Lambert,
and is being implemented, along with other work to complete the initial suite
of software. A full “Engineering Model”
of the software will be ready for testing in mid 2001. The algorithms are described in the
Algorithm Theoretical Basis Document. Ken Stone, Joseph McInerny, and James
Craft, ACD visitors and members of CLAS, are developing the operational code.
Gille and Johnson have done
extensive planning for NCAR’s roles in instrument testing (at LMSSC, beginning
early in FY 2001), calibration (at Oxford, beginning near the middle of FY
2001), and validation (after
launch). Details are contained in
numerous program documents.
Douglas Kinneson has worked
with the modeling group to extend the MOZART-3 model, extending it to 85 km
altitude, improve its dynamics, and providing global data for HIRDLS
applications. The Aura team decided to
use data from this model for testing of all Aura algorithms. Preparation and use of the model results
will take place next FY. Data from the
model were used by Gille and Lawrence Lyjak to begin to evaluate the capability
of HIRDLS data to determine small scale transport of ozone between the
stratosphere and troposphere, using meteorological data acquired for the TOPSE
program. The results with idealized
HIRDLS data showed that transports up to wave number 18 or 20 could be
resolved. This is being extended to
more realistic simulations of HIRDLS data.
Gille made a presentation on
the HIRDLS experiment at the 23rd Scientific Assembly of COSPAR in
Warsaw.
HIRDLS co-investigators
include Byron Boville (CGD), Brasseur, Michael Coffey, and William Mankin (all
at NCAR), Linnea Avallone and O. Brian Toon (University of Colorado), James
Holton and Conway Leovy (University of Washington), David Andrews, Clive
Rodgers, Fredrick Taylor, Robert Wells, John Whitney, and E. James Williamson
(all at Oxford University), Michael McIntyre and John Pyle (Cambridge
University), H.G. Muller (University of Sheffield), C.T. Mutlow (Rutherford
Appleton Laboratory), and Geraint Vaughan (University College of Wales).